Lithium metal composite oxides are used as positive electrode active materials for lithium secondary batteries. Lithium secondary cells have already been put to practical use as compact power supplies for portable telephones, notebook computers and the like. Further, the applications of lithium secondary cells in medium- and large-sized power supplies for automobile use, electric power storage use, etc. have also been attempted.
As a conventional positive electrode active material, for example, Patent Document 1 discloses a positive electrode active material for a lithium secondary cell, which uses a lithium-nickel-cobalt-manganese composite oxide represented by a composition formula LiaNi1/3Co1/3Mn1/3O2, and has a pore diameter in the range of 10 to 200 nm.